1. Field of the Invention
This invention relates to the measurement of the flow of media in pipes by the use of the Doppler frequency shift technique. In these measurements, sound waves are transmitted into the media through the wall of a pipe and are received through the wall of the pipe by means of transducers, respectively, attached to the pipe wall at preselected positions.
2. Description of the Prior Art
In FIG. 2, there is illustrated the conventional method of Doppler sonic flow measurement for measuring the flow of media in a pipe. Transducers are placed on opposite sides of the pipe and they are directed toward the media at the center of the pipe. The transmitting and receiving transducers also have the same angle of entry into the pipe, and there is no lateral offset between them. An example of such a system and method is found in U.S. Pat. No. 4,122,713 which shows in FIGS. 1 and FIG. 2 transducers disposed on opposite sides of a media conduit and the measurement of the flow rate effectively at the center of the conduit.
U.S. Pat. No. 4,062,237 shows another example of a conventional Doppler sonic flow measurement system utilizing a fixed relationship between the transmitter and receiver transducers. In this system, the measurement of flow rate in a conduit is derived using a single source and not using transducers disposed on opposite sides of the conduit. In this system, the flowmeter is capable of measuring the three-dimensional velocity vector of dynamic particles, particularly blood cells flowing in a vein. Complex electronics is then used to analyze the information received from the Doppler sonic flow measurement in order to derive the information required with respect to the flow being measured.
The use of compensating electronics for the purpose of computing average flow rates is common and often necessary in conventional systems. In other conventional systems where accuracy is not critical, the complex electronic compensation techniques have been simplified or eliminated.
In U.S. Pat. No. 4,067,236, there is shown another Doppler sonic flow measurement system which utilizes a crystal array of transducers to obtain an average flow by looking at all parts of the flow profile. In this system, there are a multiplicity of measurements, and the system does not depend upon any prior knowledge of the flow, or prediction of flow measurement points.